Back in 1995, a very famous single player and multi player game was released by ID Software called Quake. This game, along with another game called "Doom" were the top dog games being played at that time. There were a couple of other games that were quite popular as well at that time, Duke Nukem 3D and ROTT (Rise Of The Triad).
All of these games had single player story line based modes and multi player modes. They all pretty much set the industry standards and made the gaming industry take off like a Saturn 5 rocket, shaking the grounds which led to many many other "clone" type games, but all of them had the choice of single play and online play.
Around 1998, the RPG type games like WoW (World of Warcraft) began to emerge. These started out in the same way as the FPS type games, offering single play and online play.
When the 3rd edition of the QUAKE game came around..titled "Quake 3 Arena", this game was initially intended to be an online only game. Pre announcements of this stirred up plenty of angry gamers long before the game was even in it's alpha stages. ID Software was flooded with millions of letters and emails with complaints and demands that the game include an off-line mode, even to the point where gamers threatened to not buy it if it did not have the ability to run off the web, even though these upset gamers were waiting anxiously for it's release.
ID Software listened and coded the game to have off-line capability, though the game did not base itself around a story line like the previous 2 games had. Instead, the game was based on "frag-fest" and "melee-arena" aspects. The previous 2 games..Quake 1 and Quake 2 started the genre of contests of free for all melee's and rank climbing arena settings, as well as co-op contests and the most infamous.."Capture the Flag". However Quake 3 was to not have any of this except in online only modes.
ID software made the Quake 3 game single player, offline capable by keeping it's parameters of FPS frag fest/melee/arena genre, but with a twist. To have offline capability, they incorporated "bot" opponents so that a single player could play all of the game's genre modes by playing against computer controlled bots. The "bot" concept was another "after-market" add on to the previous two games, normally called "Mod's". The bots could be set up to be easy targets, or incredibly difficult opponents to hone a player's skills, sometimes even almost impossible to defeat.
The bottom line was that had ID Software not listened to the gaming community, which is the end of the line to a game's success or failure, ID Software would probably have gone out of business before the Quake 3 game was released. They learned a lesson back then, and stuck with the policy to always pay attention to the playing community that supports their business.
If this SimCity game's makers don't do what ID Software did, it will find itself left behind and abandoned, turning those simulated cities into simulated ghost towns before it is even out the door.
Basically ending up in the middle of nowhere of undeveloped landscape where nothing but dust and tumbleweeds are the norm.
They might want to learn from recent past history, or find themselves with no customers who will gladly move on to something else and not loose any sleep over it.